There have been variously proposed stencil printers where print is made by driving, for instance, a thermal head according to image data obtained by reading out an original by, for instance, a scanner to selectively melt and perforate stencil material to make a stencil, winding the stencil around a printing drum, supplying ink inside the printing drum, and transferring the ink to printing papers through the stencil by, for instance, a roller.
In the stencil printers described above, it is necessary to always hold fixed the amount of ink temporarily stored in the printing drum during printing. As such a method, there has been known a method where, for instance, the amount of ink temporarily stored in the printing drum is detected by an ink sensor and an ink supply pump is controlled according to the detecting signal of the ink sensor.
Specifically, the amount of ink stored in the printing drum can be always held fixed by temporarily storing the ink in a wedge-shaped space (ink fountain) between a cylindrical squeegee roller for applying ink on the inner peripheral surface of the printing drum and a doctor roller which is disposed in parallel to the squeegee roller at a space therefrom for passing the ink so that the ink stored in the ink fountain is supplied to the inner peripheral surface of the printing drum by way of the squeegee roller, and supplying the ink to the ink fountain from an ink container when the amount of ink in the ink fountain is reduced below a predetermined level.
When the amount of ink in the ink fountain does not reach the predetermined level if the ink supply pump is operated for a predetermined time (inkless time) after the ink sensor detects that the amount of ink in the ink fountain is reduced below a predetermined level, it is recognized that the ink container is exhausted and the system is stopped as well as the alarm representing the fact is made. Then the ink container is changed for a new one, whereby print can be further made.
In the stencil printers described above, when a plurality of kinds of ink different from each other in viscosity thereof according to the kind are available and ink lower in its viscosity than standard ink which has been employed in setting the inkless time is employed, that the predetermined amount of ink is supplied is not detected by the ink sensor and the inkless time can expire even if the predetermined amount of ink is supplied since the swirl of the ink generated in the ink fountain is low. In this case, there is a fear that the ink container which yet holds ink therein can be detected as an empty ink container by mistake. Accordingly, it is necessary to elongate the inkless time when the above-mentioned ink is used. Whereas, when ink higher in its viscosity than standard ink which has been employed in setting the inkless time is employed, the time required to be detected by the ink sensor becomes shorter than the standard ink since the swirl of the ink generated in the ink fountain is higher. If the inkless time is elongated when such ink is used, a wasteful long time is required until the operator knows that the ink container is exhausted.
When a ceasing time from interruption of printing and resumption of the same is elongated, the water content and/or solvent of the ink in the ink fountain evaporates to reduce the amount of ink and accordingly, it is necessary to elongate the inkless time by the reduction of the amount of ink when printing is resumed.
Accordingly, it has been proposed to set the inkless time according to the kind of ink or to set the inkless time according to the ceasing time in the stencil printer. (Japanese Unexamined Patent Publication No. 9(1997)-39363)
However, when the inkless time is set in advance in the stencil printer according to the kind of ink, a suitable inkless time cannot be set if the kind of ink which has not been set in the stencil printer is employed, which gives rise to the above-mentioned problem of mistake in detection or the like.
In view of the foregoing observations and description, the primary object of the present invention is to provide a method, a system and an ink container which, in those where the ink is automatically supplied in the stencil printing, permit suitable setting of the inkless time even if the kind of ink which has not been set is employed.